Learning Forum

[NeilZA]

I want to perform an analysis on a steel frame which is anchored onto a concrete floor and wall (concrete not simulated in model). See picture included, grey area represents concrete and red crosses represents anchors.

[peteroznewman]

There are several ways to accomplish this.nThe first is to leave out the extra constraint. How far does the steel move into the concrete?nThe simplest way is to add a Compression Only Support. Behind the scene, it copies the surfaces that were selected and turns them into invisible rigid surfaces that have a frictionless contact with the body. You might need to control the Initial Step Size for Auto Time Stepping under Analysis Controls to get this working.nThe next method is to do that work yourself, but then you can make the copy of the surface larger and use friction.nn

[NeilZA]

nThanks for your response.nI am planning to conduct a response spectrum analysis on the model and have not yet completed the simulation, so I do not know how much the beams deflect into the concrete space. I am however afraid that if I do not constrain the vertical beams in the direction of the concrete, it would result in an unrealistic modal analysis. nI have just tried applying Compression Only Supports, but see that it can only be applied on faces. My model is a simplified line body model. Any ideas how to apply a similar constraint on line bodies?n

[peteroznewman]

Response Spectrum is a Linear Analysis. That means no nonlinear behavior is allowed. You can't use Compression Only support or any other kind of nonlinear contact. You can use linear constraints that allow sliding, such as a Joint. You could have a General Joint to ground that only constrains the motion of a vertex in X displacement, but allows freedom in all other DOF.nDo the Modal Analysis and Response Spectrum without any extra supports, then repeat with extra supports if the outcome of the first analysis is excessive response.n

[NeilZA]

thanks again. I agree with your proposal, I'll perform the analysis without additional constraints and adapt if necessary.n